Procedure for hardening at least one surface of a wall of a component and device for its execution

ABSTRACT

A procedure for hardening at least one surface (S, L) of a wall (W) of a component (T), in which the surface to be hardened (S, L) is inductively heated with at least one inductor ( 2 ), in which liquid is filled into a gap (P) between the surface to be hardened (S, L) and the inductor ( 2 ) while heating the surface to be hardened (S, L), in which the side (AS) of the wall (W) opposite the side (IS) of the wall (W) provided with the surfaces to be hardened (S, L) is sprayed with liquid while heating the surface to be hardened (S, L), and in which at least one liquid jet (KI) is aimed at a zone (RZ) of the wall (W) that is adjacent to the surface to be hardened (S, L), and to be precluded from heating by the inductor ( 2 ). The procedure according to the invention makes it possible to tailor the hardening of at least one surface to the respective requirements, even on the walls of complexly shaped components with a small wall thickness.

BACKGROUND OF THE INVENTION

The invention relates to a procedure for hardening at least one surfaceof a wall of a component and a device specially suited for executingthis procedure.

The problem when hardening surfaces on walls of components is that theobjective is to achieve the desired quality of hardening on the onehand, while preventing the wall in question from losing the toughnessrequired for the respective application of the component. Therefore, itis necessary to prevent the wall from becoming heated through whileheating the surfaces to be hardened.

This can be accomplished during the use of inductors, which heat thesurfaces to be hardened by inducing an electromagnetic field, by settingthe penetration depth of the field generated by the inductor accordingto the required depth of hardening in the area of the surface to behardened. However, this process presumes that a sufficient wallthickness is present in the area of the surface to be hardened.Otherwise, the wall cannot be prevented from heating through, and hencehardened through due to heat migration.

Therefore, when hardening of relatively thin-walled components, a changehas been made in practice to cooling with liquid the wall lying oppositethe side of the wall having the surfaces to be hardened, By suitablymetering the cooling liquid stream, the penetration depth of the heatgenerated in the wall by the inductor, and hence the depth of hardeningin the area of the surface to be hardened, can be set even in thinwalledcomponents.

Special requirements are placed on the hardening of surfaces on thewalls of a component with respect to front-drive motor vehicles, inwhich the drive torque is transferred via sliders, which sit moveably ina so called “tripod”. Such a tripod is shaped like a bowl, and exhibitsseveral supporting and running surfaces angled relative to each otherand extending in a longitudinal direction, axially parallel to thelongitudinal axis of the tripod. The sliders arc guided on thesesupporting and running surfaces. At the same time, the supportingsurfaces absorb the torque transferred by the sliders. To be able towithstand this load, the supporting and running surfaces must behardened. At the same time, the toughness of the wall material must beretained, despite the hardening of the surfaces, so that the tripod canwithstand the alternating torque loads while driving the vehicle.

The object of the invention is to provide a procedure of the kinddescribed above, which enables a hardening of at least one surfaceadapted to the respective requirements, even on the walls of complexlyshaped components with a small wall thickness. In addition, a devicesuitable for executing this procedure is to be specified.

SUMMARY OF THE INVENTION

This object is achieved in terms of the procedure for hardening at leastone surface of a wall of a component by virtue of the fact that thesurface to be hardened is inductively heated with at least one inductor,that a liquid is filled in a gap present between the surface to behardened and the inductor while heating the surface to be hardened, thatthe side of the wall lying opposite the side of the wall provided withthe surfaces to be hardened is applied with liquid as the surface to behardened is heated, and that at least one liquid jet is aimed at a zoneof the wall adjacent to the surface to be hardened, which is to beprevented from being heated by the inductor.

According to the invention, not only is the side of the wall lyingopposite the side of the wall provided with the surface to be hardenedwetted with cooling liquid, but liquid is additionally aimed at the zoneof the side of the wall that borders the surface to be hardened, and isnot to be encompassed by hardening. The additional liquid jet transportsaway the heat that arises in the zone to be excluded from heating due tothe influence of the induced electromagnetic field. In this way, notonly the penetration depth of the hardening zone can be specificallypredetermined in the area of the surfaces to be hardened, also itssurface expansion can.

Therefore, the procedure according to the invention makes it possible toform precisely delineated hardening zones, whose expansion and depth areadapted to the respective structural requirements and loads of thecomponent provided with the hardened surfaces. For example, aprogression of the edge of the hardened surfaces established preciselybased on the orientation and progression of the liquid jets can begenerated by virtue of the fact that the liquid jets are each aimed atthe wall provided with the surface to be hardened in sections or in aspecific sequence, and transport away the heat arising there. In thisway, for example, a sufficiently soft wall material can be provided atprecisely the locations where deformation is to be executed afterhardening the wall surfaces for structural or assembly-related reasons.

At the same time, because the gap between the inductor and surface to behardened is filled with liquid, the field generated by the inductorpenetrates into the wall to be heated in a uniform fashion. In this way,a homogeneous processing result can be ensured, even though streams ofcooling liquid are continuously supplied while heating the surfaces thatwould otherwise disrupt the uniformity of heating.

The procedure according to the invention is particularly suited forhardening surfaces on walls of those components in which the wallenvelops an interior space, and the surfaces to be hardened are arrangedon the side of the wall allocated to the interior space. The uniformfilling of the gap between the inductor and surface to be hardened canbe ensured in a particularly simple manner in these types of components.Additionally in structural members designed like this, several surfacescan be hardened simultaneously. This also applies in particular in caseswhere at least two adjacent surfaces angled relative to one another areeach hardened at the same time, as is the case with respect to thetripods described at the outset, for example.

One particularly intensive, short-term inductive heating of the surfaceto be hardened limited to a specific, narrowly delineated surface anddepth can be achieved by generating the electromagnetic field at highfrequency. In this way, the inductive heating of the surfaces to behardened can advantageously take place at a frequency of up to 80 kHz,for example.

A device particularly well-suited for executing the procedure accordingto the invention is equipped with an inductor for heating the surface tobe hardened, a liquid feed line, through which liquid gets into the gapbetween the inductor and the surface to be hardened, a first sprayer,which aims at least one liquid jet at the side of the wall lyingopposite the side of the wall provided with the surface to be hardened,and with at least one additional sprayer, which aims the liquid jet atthe zone of the wall to be precluded from hardening.

In this case, it is particularly beneficial if the sprayer whose jet isaimed at the zone to be precluded from hardening be carried by theinductor. This type of design of the device according to the inventioncan be realized with a low technical outlay, and yields a compact shapefor the required structural members. The latter is always of particularimportance in cases where only a little space is available inside thedevice for the inductor and sprayers.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantageous developments of the procedure according to theinvention and device suitable for its execution are given in thesubclaims, and shall be described in greater detail below in conjunctionwith an embodiment based on the drawing. Shown on:

FIG. 1 is a device for hardening the supporting and running surface of atripod, longitudinal section;

FIG. 2 is a section “X” of FIG. 1, magnified scale;

FIG. 3 is the device according to FIG. 1, cross section;

FIG. 4 is the tripod in a section corresponding to the A-B line penciledin on FIG. 3;

FIG. 5 is the tripod in a section corresponding to the C-D line penciledin on FIG. 3;

FIG. 6 is the tripod after upsetting deformation that takes placefollowing the hardening of the supporting and running surfaces, in asection corresponding to the A-B line penciled in on FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The device 1 for hardening the supporting surfaces S and the runningsurfaces L of a tripod T exhibits an inductor 2, an outside sprayer 3, afront surface sprayer 4 and a work piece holder 5.

The tripod T is shaped like a bowl, and exhibits a wall W that envelopsan interior space I and stands on a floor B. Groove-like guide paths Ffor the sliders (not shown) are incorporated in the wall W proceedingout from the interior space 1, each offset by 120° with a star-shapedcross section, and extend axially parallel to the longitudinal axis X ofthe tripod T. The corner areas E1, E2 of these guide paths F eachincorporate a running surface L and a supporting surface S at a rightangle to each other in cross section, wherein the supporting surface Sis curved, reflecting the shape of the sliders (not shown).

The outer shape of the inductor 2 that can be lifted and lowered in itslongitudinal direction is adapted to the shape of the interior space Iof the tripod T in such a way that the inductor 2 engages the guidepaths F of the tripod T with a radially projecting section. In thiscase, the dimensions of the inductor 2 are such that a continuous gap Pis present between the outer border 7 of the inductor 2 and the insideIS of the wall W of the tripod T with the inductor 2 introduced into thetripod T.

The corner regions of the projecting sections of the inductor 2allocated to the corner regions E1, E2 of the guide paths F are eachformed by a heating resistor 10 with the required sheeting 11. Inaddition, a supply pipe 12 for cooling liquid is positioned coaxially tothe longitudinal axis Y of the inductor 2. The supply pipe 12 isconnected with a liquid feed (not shown), and empties on the front side13 of the inductor 2. Liquid additionally exits into the free paces ISremaining between the heating resistors 10 or sheeting 11 via channels14 radially branching from the supply pipe 12.

Incorporated in the upper part of the inductor 2 in each of the radiallyprojecting sections of the inductor 2 is a channel 16, which isconnected with the liquid feed (not shown), just as the supply pipe 12.In this case, the channels 16 are each allocated to the supportingsurfaces S of the guide paths F of the tripod T. Spheroidised into theouter wall 17 of the channels 16 are radially outwardly projectingoutlet holes 19, which are each oriented toward the edge zone RZ of theinside IS of the wall W of the tripod T situated between the upper edgeR of the wall W and the upper edge of the supporting surface S to behardened with the inductor 2 introduced into the tripod T. In this way,a sprayer 20 is formed on the inductor 2, which aims liquid jets KI atzones RZ of the tripod T that are directly adjacent to the surfaces tobe hardened and to be precluded from hardening.

The outside sprayer 3 is ring-shaped, and its inner wall 32 providedwith uniformly arranged outlet holes 31 envelops the tripod T standingon the work piece holder 5. Situated between the outer wall 33 and innerwall 32 of the outside sprayer 3 is a channel 34, which is alsoconnected with the liquid feed (not shown).

The front surface sprayer 4 is carried by the inductor 2, so that it canbe lowered or lifted by the latter in the direction of tripod T. Theshape of the front surface sprayer 4 is adapted to the progression ofthe upper edge R of the tripod T in such a way that its lower face 41runs adjacent to the front face of the upper edge R of the tripod T.Outlet holes 42 oriented toward the edge R of the tripod T arerespectively spheroidised in the front surface 41 in the sections of thefront surface sprayer 4 that are allocated to the supporting surfaces S,the wall sections Wa between the guide paths F and the unhardened wallsections Fa of the guide paths F between the running paths L. (Forpurposes of clarity, only half the front surface sprayer 4 is shown onFIG. 3.)

In order to harden the supporting surfaces S and running surfaces L ofthe tripod T, the inductor 2 is lowered into the interior space I of thetripod T. In this lowered position, the outlet of supply pipe 12 islocated a slight distance away from the floor B of the tripod T. Thefront surface sprayer 4 is also spaced apart from the edge R of thetripod T. The outlet nozzles of the sprayer 20 are oriented toward thesection of the edge area RZ of the tripod T respectively oriented tothem.

Subsequently, the outside sprayer 3, the front surface sprayer 4 and thesprayer 20 along with the supply pipe 12 are impacted with coolingliquid from the liquid feed (not shown), so that cooling liquid jets KAcool the outside AS of the wall W, cooling liquid jets KR cool thesections of the face allocated to the outlet holes 42 of the frontsurface sprayer 4 in the area of the upper edge R of the wall W, andcooling jets KI cool the edge zones RZ of the wall W of the tripod Timmediately adjacent to the supporting surfaces S to be hardened. Thecooling liquid exiting the outlet of the supply pipe 12 and the channels14 branching from the supply pipe 12 fills the gap 8 present between thewall W and the inductor 2.

The supporting and running surfaces S, L of the guide paths F are theninductively brought to the temperature necessary for the desired heatingthrough exposure to the electromagnetic field generated by the heatingresistors 10. After heating is completed, the heated running surfacesare quenched by the cooling liquid stream exiting the supply pipe 12.The hardening zone HL then present in the area of the running surfaces Lextends in a longitudinal direction up to under the edge R of the wallW, since no cooling jets KI have been sent out by the sprayer 20 in thisarea. By contrast, in the area of the supporting surfaces S, the edgezone RZ remained unhardened between the accompanying hardening zone HSand the edge R, since cooling via the cooling liquid jets KI was activein this zone during the heating of the supporting and running surfacesS, L. Due to the cooling of the outside AS of the wall W, the depth t ofboth hardening zones HL, HS is limited to roughly half the wallthickness of the wall W.

After the sliders (not shown) have been mounted in the tripod T, thetripod T is subjected to upsetting deformation in a device (also notshown), as a result of which a bead U projecting inside the interiorspace I of the tripod T is generated in the area of the unhardened edgezone RZ. This bead prevents the sliders mounted in the tripod T fromfalling out.

KEY

1 Hardening device

2 Inductor

3 Outside sprayer

4 Front surface sprayer

5 Work piece holder

7 Outer delineation of inductor 2

10 Container

11 Sheeting

12 Supply pipe

14 Channels

13 Front side of inductor 2

15 Free spaces

16 Channels

17 Outer wall of channels 16

19 Outlet holes

20 Sprayer

31 Outlet holes

32 Inner wall

33 Outer wall

34 Channel

41 Front surface

42 Outlet holes

AS Outside of wall W

B Floor

E1,E2 Corner areas

F Guide paths

Fa Wall sections

HL,HS Hardening zones

I Interior space

IS Inside of wall W

KA Cooling liquid jets

KI Liquidjets

KR Cooling liquid jets

L Running surfaces

P Gap

R Edge

RZ Edge zone

S Supporting surfaces

T Tripod

t Depth of hardening zones HL, HS

U Bead

W Wall

Wa Wall sections

X Longitudinal axis of tripod T

Y Longitudinal axis of inductor 2

What is claimed is:
 1. A procedure for hardening at least one surface(S, L) of a wall (W) of a component (T) in which the surface to behardened (S, L) is inductively heated with at least one inductor (2), inwhich, while heating the surface to be hardened (S, L), a liquid isfilled into a gap (P) present between the surface to be hardened (S, L)and the inductor (2), in which, during the heating of the surfaces (S,L) to be hardened, a liquid jet (KA) emitted from a sprayer (3) is aimedat the side (AS) of the wall (W) lying opposite the side (IS) of thewall (W) provided with the surfaces to be hardened (S, L), and in whichat least one liquid jet (KI) emitted from an additional sprayer (20)carried by the inductor (2) is aimed at a zone (RZ) of the wall (W) thatis adjacent to the surface to be hardened (S, L), and to be precludedfrom heating by the inductor (2).
 2. The procedure according to claim 1,wherein the wall (W) envelops an interior space (1), and that thesurface to be hardened (S, L) is arranged on the side (IS) of the wall(W) allocated to the interior space (I).
 3. The procedure according toclaim 1, wherein the component (T) is shaped as a bowl.
 4. The procedureaccording to claim 1, wherein at least two adjacent surfaces (S, L)angled relative to each other are hardened at the same time.
 5. Theprocedure according to claim 1, wherein the zone (RZ) of the wall (W)precluded from heating is arranged between an edge (R) of the wall (W)and the surface to be hardened (S, L).
 6. The procedure according toclaim 5, wherein liquid is applied to the edge (R) of the wall (W) whileheating the surfaces to be hardened (S, L).
 7. The procedure accordingto claim 1, wherein the component (T) is subjected to upsettingdeformation after hardening the surfaces to be hardened (S, L), as aresult of which a bead (W-V is formed in the area of the zone (RZ)precluded from hearing.
 8. The procedure according to claim 7, whereinthe wall (W) envelops an interior space (I), and wherein the bead (U) isoriented in the interior space (I).
 9. The procedure according to claim1, wherein the surfaces to be hardened (S, L) are inductively heated ata frequency of up to 80 kHz.
 10. A device for executing the procedureaccording to claim 1, with an inductor (2) for heating the surface to behardened (S, L), with a liquid feed (12), through which liquid gets intothe gap (P) between the inductor (2) and the surface to be hardened (S,L), with a first sprayer (3), which aims at least one liquid jet (KA) onthe side (AS) of the wall (W) lying opposite the side (IS) of the wall(W) provided with the surface to be hardened (S, L), and with at leastone additional sprayer (20), which is carried by the inductor (2), andaims a liquid jet (KI) at the zone (RZ) of the wall (W) that is adjacentto the surface to be hardened (S, L) and to be precluded from hardening.11. The device according to claim 10, wherein the liquid feed isdesigned as a liquid line (12) arranged in the inductor (2) that ends onone side (13) of the inductor (2).
 12. The device according to claim 11,wherein the liquid line (12) runs axially parallel and closely adjacentto the heating resistors (10) of the inductor (2).
 13. The deviceaccording to claim 12, wherein the liquid line (12) is arrangedcoaxially to the longitudinal axis (Y) of the inductor (2).
 14. Thedevice according to claim 12, wherein the liquid line (12) ends on afront side (13) of the inductor (2).
 15. The device according to claim14, wherein a channel (16) is incorporated in the inductor (2) whichsupplies the sprayer (20) with liquid.
 16. The device according to claim10, wherein the inductor (2) exhibits several heating resistors (10)arranged axially parallel to a longitudinal axis (Y).
 17. The deviceaccording to claim 10, wherein an additional sprayer (4) aims a liquidjet (KR) at an edge (R) of the wall (W) provided with the surfaces to behardened (S, L).
 18. The device according to claim 17, wherein theadditional sprayer (4) is coupled with the inductor (2).